As described in the MR Reinhausen Manufacturing (Box 96, Alamo Tenn. 38001) brochure (RM03/90-1090/3000) "Load Tap Changer Type RMV-1" it is standard to actuate the vacuum interrupter in a load tap changer with a cam-action linear spring-loaded mechanism that moves the interrupter actuating rod in one direction to close the interrupter and in the opposite direction to open it. Each phase is controlled by one such vacuum interrupter and the actuator has a slide that moves on stationary tie rods. The slide itself is moved on the rods by engagement between a roller it normally carries that rides in a groove in a noncircular cam on the main drive shaft of the load switch.
Since the cam rotates it does not exert force exactly in the linear direction defined by the tie rods carrying the slide. Thus friction is considerable, and jamming is possible.
Various solutions have been proposed, for example in German patent 2,002,054 based on U.S. application Ser. No. 792,349 of D. White, German patent 2,021,575 filed 02 May 1970 by K. Fricke et al, German patent 2,806,282 filed 15 Feb. 1978 by W. Breuer, German patent 3,919,596 based on Japanese applications files 15 Jun. 1988 by S. Ogawa, and German patent 4,011,019 filed 05 Apr. 1990 by D. Dohnal et al. None of these systems constitutes a wholly satisfactory solution to the problem of making the actuator jam- and friction-free.